The chromatin-associated proteases of testicular seminiferous epitheleal cells of the rat will be isolated, purified, and characterized. These proteases will be assayed versus (3H) labeled histones and various synthetic chromogenic and fluorogenic peptides. The relative concentrations and enzymatic activities of the chromatin-associated proteases will be determined in nuclei of pachytene primary spermatocytes in relation to the possible role of these proteases in removal of excess histones. A study will be made of the possible role of these proteases in removal of histones for replacement by protamines in spermatids, and the involvement of hormones in this process will be examined.